Footwear article with pressure sensor

ABSTRACT

An article of footwear including a pressure sensor arranged in the sole structure, where the sensor includes elongated pressure-sensing cells, each of which has an axis of main extension, each cell having a first and a second carrier film, which are attached to one another by a spacer film having an elongated opening oriented along the axis of main extension, as well as a first and a second electrode on the first and the second carrier film, respectively, where the electrodes are arranged in facing relationship with each other, so that a contact area between them increases with increasing pressure, and an electrically insulating layer is arranged within the opening having a shape such that it locally prevents direct contact between the electrodes where the insulating layer is present and enables the direct contact where it is absent, where the shape is constant or repetitionary along the axis of main extension of the cell.

TECHNICAL FIELD

The present invention generally relates to an article of footwear, suchas e.g. a shoe, a boot, a sandal or the like, in particular an articleof footwear equipped with a pressure sensor for measuring pressureexerted by the wearer's foot on the sole structure.

BACKGROUND ART

Document U.S. 2010/0063779 discloses a shoe with an integrated sensorsystem. The sensor system collects performance data that are transferredfor further use via a communication port. The shoe contains a forcesensor arranged in the sole structure for measuring, in a plurality ofareas, pressure (force) exerted by the wearer's foot on the solestructure, and an electronic module configured to gather data from thesensors. The module is configured for transmitting the data to anexternal device for further processing. In one of the embodimentsdisclosed in U.S. 2010/0063779, the pressure sensor comprises fourelongated pressure-sensing cells, each of which contains a first and asecond electrode as well as a force-sensitive resistive materialdisposed between the electrodes to electrically connect the electrodestogether. When pressure is applied to the force-sensitive material, itsresistivity changes, and the resulting change in resistance is detectedby the electronic module. Materials exhibiting volume-based resistancebehavior are used as the force-sensitive material: when such material iscompressed, conductive particles contained therein move closer together,whereby conductive paths are formed and the resistance decreases. Ifanother resistance vs. pressure characteristic is needed, a suitableforce-sensitive material has to be found, which may be difficult.

BRIEF SUMMARY

The disclosure provides an article of footwear including a pressuresensor, wherein the resistance vs. pressure characteristic of thepressure sensing cells enables more flexible adjustments.

The proposed article of footwear (in particular a sports shoe, such ase.g. a running shoe, a tennis shoe or the like) comprises a solestructure for supporting a wearer's foot, an upper for holding thewearer's foot onto the sole structure and a pressure sensor arranged inthe sole structure for measuring a pressure exerted by the wearer's footon the sole structure. The pressure sensor comprises one or moreelongated pressure-sensing cells, each of which has an axis of mainextension. Each cell comprises a first flexible carrier film and asecond flexible carrier film, the first and second carrier films beingattached to one another by a spacer film having an elongated openingoriented along the axis of main extension, a first electrode arranged onthe first carrier film and a second electrode arranged on the secondcarrier film, the first and second electrodes being arranged in facingrelationship with each other in the opening, in such a way that thefirst and second electrodes may be brought into contact with each otherwhen pressure is exerted on the cell and that a contact area between thefirst and second electrode increases with increasing pressure. Accordingto the invention, an electrically insulating layer is arranged withinthe opening of the spacer. The electrically insulating layer has a shapesuch that it locally prevents a direct contact between the first andsecond electrodes where the electrically insulating layer is present andenables the direct contact where the electrically insulating layer isabsent. The shape of the electrically insulating layer is constant orrepetitionary along the axis of main extension of the cell.

The above-described shape of the electrically insulating layerascertains that the response of the pressure sensing cell remains atleast approximately the same when the point of application of the force(and thus the area of contact between the elements on the first carrierfilm and the elements on the second carrier film) is displaced along theaxis of main extension of the cell. In other words, the response of thepressure sensing cell is at least approximately invariant under atranslation along the axis of main extension of the point of applicationof the force (within the boundaries of the cell). Those skilled in theart will appreciate that this feature will render pressure sensing lessdependent on the size of the wearer's foot by suitably positioning andorienting the pressure-sensitive cell(s) in the sole structure. As aconsequence, a pressure sensor as used in the context of the inventionmay be suitable for footwear of different sizes.

Preferably, the one or more elongated sensor cells are located in thesole structure in areas expected to be subjected to pressure maxima whenthe wearer is standing still, is walking or is running. Advantageously,each sensor cell is located in an area corresponding to a bone or partof bone of a wearer's foot selected from the heel bone, the head of thefirst metatarsal bone, the head of the fourth or fifth metatarsal bone,the head of the second or third metatarsal bone and the head of thefirst phalange. Those skilled will appreciate that pressure maxima aretypically located under the heel bone, under the heads of the fourthand/or fifth metatarsal bone and under the head of the first phalangewhen the wearer is standing at rest; when the wearer is walking, thepressure maxima are usually under the heel bone, under the heads of thesecond and/or third metatarsal bone and under the head of the firstphalange.

Preferably, the axis of main extension of each cell is oriented along anaxis of main extension of a vertical projection onto the sole structureof the bone to which it corresponds.

The pressure sensing cells are preferably oval, elliptical orrectangular with rounded angles.

According to a preferred embodiment of the invention, the shape of theelectrically insulating layer comprises a sequence of generallytriangular tooth portions arranged in the manner of a toothed rack inparallel with the axis of main extension.

Preferably, at least one of the first and second electrodes is made ofresistive material, e.g. graphite or carbon black. The electricallyinsulating layer is preferably made of electrically insulating ink.

For equalization of gas pressure inside the opening, each of thepressure sensing cells advantageously comprises a ventilation hole. Theventilation hole may be in fluid communication with the exterior of thepressure sensor (e.g. the atmosphere) or with a gas (e.g. air) reservoirwithin the pressure sensor. Such gas reservoir could e.g. be a cavitybetween the first and second carrier films.

As those skilled will appreciate, the pressure sensor could be arrangedin different part of the sole structure. For instance, the pressuresensor being arranged on or in the insole. Alternatively, the pressuresensor may be arranged on or in the midsole.

According to a preferred embodiment, the one or more pressure-sensingcells are at least two pressure-sensing cells. The pressure sensor inthis case preferably comprises one or more connection stripsinterconnecting the at least two pressure sensing cells, the one or moreconnection strips being integrally formed with the at least two pressuresensing cells. The connection strips preferably bear conductors forconnecting the first and second electrodes of each pressure-sensing cellwith an electronic control module. The connection strips are preferablyconfigured having a serpentine shape in order to offer a greaterresiliency to the pressure sensor as a whole.

Preferably, the pressure-sensing cells are configured (in particular bytailoring of the shape of the electrically insulating layer) in such away that pressures in the range from about 0.1 bar to 7 bar translateinto a steady change of the contact area between the resistiveelectrodes from 0% (at the turn-on pressure, i.e. at the about 0.1 bar)and about 100% (full contact at about 7 bar).

A preferred embodiment of a pressure sensor for an article of footwearcomprises a flexible multilayer film structure that includes a forefootportion and a heel portion. The forefoot portion and the heel portionare connected to each other by a connection strip, which is integrallyformed with the multilayer film structure. According to this embodiment,the pressure sensor further comprises a trough-shaped receptacle for anelectronic control module, which the connection strip is arranged acrossand which the connection strip is bonded to. This embodiment of apressure sensor for an article of footwear has the advantage thatstresses occurring in the middle region of the article of footwearduring rolling off of the foot are at least partially taken up by thereceptacle instead by the connection strip. Additionally, buckling ofthe pressure sensor is efficiently avoided in this region of the articleof footwear.

Preferably, the trough-shaped receptacle is made of plastic material,e.g. PET or epoxy. The edges of the receptacle are preferably roundedwhere the connection strip crosses them in order to avoid that theconnection strip is cut off under the action of mechanical loads.

Advantageously, in the connection strip, the upper (second) carrier filmof the pressure sensor is interrupted and detached from the spacer filmand the first carrier film in such a way that a tongue or flap isformed, that tongue or flap carrying connection terminals forelectrically connecting the multilayer film structure (in particular thepressure-sensing cells thereof) to the electronic control module.Preferably, the tongue or flap is equipped with a crimp connectorportion for releasable connection with the electronic control module.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way ofexample, with reference to the accompanying drawings in which:

FIG. 1 is a longitudinal cross sectional view of the sole structure of asports shoe with a pressure sensor;

FIG. 2 is a top view of the pressure sensor of the sports shoe of FIG.1;

FIG. 3 is a top schematic view of one of the pressure sensing cells ofthe pressure sensor of FIG. 2;

FIG. 4 is a schematic cross sectional view of the B-B plane of FIG. 3;

FIG. 5 is a graph illustrating the difference in the electricalresponses of a pressure-sensing cell without an electrically insulatinglayer and one with such a layer;

FIG. 6 is a block diagram of the electrical circuit of the pressuresensor illustrated in FIG. 2;

FIG. 7 is a schematic block diagram of an alternative electrical circuitfor the pressure sensor of FIG. 2;

FIG. 8 is a schematic block diagram of another alternative electricalcircuit for the pressure sensor of FIG. 2;

FIG. 9 is a top schematic view of the components on the first carrierfilm in a pressure-sensing cell according to another configuration;

FIG. 10 is a top schematic view of the components on the second carrierfilm in a pressure-sensing cell according to that configuration;

FIG. 11 is a top view of a variant of the pressure sensor of FIG. 2;

FIG. 12 is a schematic cross sectional view of the C-C plane of FIG. 11.

DETAILED DESCRIPTION

An article of footwear, in form of a sports shoe 10 is depicted in FIG.1 as including an upper 12 and a sole structure 14. The upper 12 issecured to sole structure 14 and defines chamber for receiving a foot.The sole structure 14 includes an outsole 14.1, a midsole 14.2, and aninsole 14.3, which forms the bottom of the foot-receiving chamber of thesport shoe 10.

In the illustrated embodiment, the midsole 14.2, which is preferablyformed of impact-attenuating material, has a film-type pressure sensor16 attached to its upper surface. When the insole is in place, thepressure sensor 10 is thus sandwiched between the insole 14.3 and themidsole 14.2.

As best shown in FIG. 2, the pressure sensor 16 comprises a plurality ofpressure-sensing cells 18, located in different areas of the solestructure 14, for measuring pressure exerted by the wearer's foot on thesole structure 14.

The configuration of the pressure sensing cells 18 will now be describedwith reference to FIGS. 3 and 4. FIG. 3 shows the contours of theelements of a pressure-sensing cell 18. The pressure sensor 16 comprisesa multilayered structure including a first carrier film 20, a secondcarrier film 22, and a spacer 24. The spacer 24 is typically adouble-sided adhesive, with which the first and second carrier films 20,22 are laminated together. The first and second carrier films 20, 22 arepreferably made of PET but other materials such as PEN, PI, PEEK etc.are also possible. Each of the carrier films may comprise a single filmlayer or comprise a plurality of film layers of the same or differentmaterials. The spacer 24 preferably comprises a PET, PEN, PI, PEEK, etc.film layer with an adhesive coating applied on each side thereof. Ateach pressure-sensing cell 18, the spacer comprises an oblong opening26, within which the first and second carrier films 20, 22 may bepressed together. In each pressure-sensing cell 18, a first resistiveelectrode 28 is permanently arranged on the first carrier film 20 and asecond resistive electrode 30 is permanently arranged on the secondcarrier film 22, in facing relationship with the first electrode 28.Each electrode 28, 30 is contacted by a respective strip conductor 34,36, which run alongside the long sides of the opening 26. At least oneof the electrodes 28, 30 (in this example: electrode 28) is partiallycovered with an electrically insulating layer 32 (e.g. a dielectriclayer).

In response to pressure acting on the pressure-sensing cell, at leastone of the first and second carrier films 20, 22, deflects towards theother carrier film until the carrier films 20, 22 or the elements ontheir respective surface come into contact. Once contact is established,the radius of the mechanical contact surface increases with increasingpressure. When a direct contact is established between the electrodes 28and 30, the electrical resistance between the conductors 34 and 36becomes finite and a current may flow in consequence. As the contactarea between the first and second electrodes 28, 30 increases, theresistance measurable between the conductors 34 and 36 decreases. Thepositions of the contacts between the resistive electrodes 28, 30 andthe respective strip conductor 34, 36, the specific resistance of theresistive electrodes, and the shape of the electrically insulating layer32 determines the pressure-dependent cell resistance.

The electrical response function of the pressure-sensing cells, i.e. theresistance versus pressure, may be adjusted in a predetermined manner bysuitably shaping the insulating layer 32, because the electricallyinsulating layer 32 locally prevents a direct contact between the firstand second electrodes 28, 30 whereas the direct contact is possible inthose areas where the electrically insulating layer 32 is absent. Theother parameters of the pressure-sensitive cells, e.g. the materials ofthe electrodes, need not be adapted. FIG. 5 schematically illustratesthe difference in the electrical response of a pressure-sensing cellwithout the insulating layer (dotted curve 38) and one with theinsulating layer shaped as in FIG. 3 (continuous curve 40), all othercell parameters being the same. One notes that for the pressure-sensingcell without the insulating layer the resistance change occurs in arelatively small pressure range starting at the activation pressurep_(act) (the pressure at which the electrodes enter into contact). Abovep_(act), the resistance quickly levels out at a low value. For the cellequipped with the insulating layer, the resistance change spreads over asignificantly longer pressure interval. As a consequence, the cell withthe insulating layer enables pressure measurement at significantlyhigher pressures than the cell without the insulating layer.

The shape of the electrically insulating layer 32 being constant orrepetitionary along the axis of main extension A, the electricalresponse of the cell 18 will be substantially independent of the exactposition on axis A of the point of application of the compressive force.In the illustrated embodiment, the electrically insulating layer 32comprises a sequence of generally triangular tooth portions 42 arrangedin the manner of a toothed rack disposed in parallel with the axis ofmain extension A. As best illustrated in FIG. 2, the pressure-sensingcells 18 are arranged in areas of the shoe 10, in which the pressurepeaks are expected to occur when the wearer is standing, walking orrunning. Specifically, a first one of the pressure-sensing cells ispositioned in the area of the head of the first phalange (big toe), asecond one in the area of the head of the first metatarsal bone, a thirdone in the area of the head of the fifth metatarsal bone and a fourthone in the area of the calcaneum (heel bone). The axis of main extensionof each cell 18 essentially corresponds to the vertical projection ontothe sole structure of an axis of main extension of the bone, which thecell is associated with. This renders pressure sensing in the cells lessdependent on the size of the wearer's foot. In fact, the describedarrangement of the pressure-sensing cells is tolerant, up to a certainextent, regarding discrepancies between the nominal shoe size, which thepressure sensor has been designed for, and the actual size of thewearer's foot. This size tolerance makes it possible to use one size ofpressure sensor for a range of shoe sizes (e.g. three consecutive shoesizes in the Continental European system).

For fixation of the pressure sensor 16 to the sole structure 14 (in thisexample the midsole), the pressure sensor 16 comprises one or morefixation pads 44 (see FIG. 2). The fixation pads 44 preferably comprisea layer of pressure-sensitive or heat-activatable adhesive, initiallyprotected by a release liner, which is removed just before the pressuresensor 16 is attached to its carrier member of the sole structure 14.

The pressure sensor 16 further comprises an electronic control module46, which is mechanically attached to the multilayer film structure ofthe pressure-sensor 10. Connection strips 48 interconnect the pressuresensing cells 18 and the electronic control module 46. The connectionstrips 48 are integral part of the multilayer film structure of thepressure sensor 16 and carry conductive tracks that electrically connectthe first and second electrodes of each pressure-sensing cell 18 withthe electronic control module 46. One or more of the connection strips48 have a serpentine shape to act as springs and to thereby increase thepressure-sensor's elasticity in the sensor plane.

The electronic control module 46 preferably comprises anapplication-specific integrated circuit (ASIC), a field-programmablegate array (FPGA), a microprocessor, or the like. Advantageously, theelectronic control circuit is configured for wirelessly transmitting thecollected pressure data or any data derived therefrom to a receiverappliance having a user interface. Such receiver appliance could includea (wrist-) watch, the wrist receiver of a heart rate monitor, a handheldcomputer, a mobile phone, a portable media player or the like. In theillustrated embodiment, the electronic control module 46 is arranged ina cavity or well of the midsole 14.2. The cavity or well may be locatedelsewhere in the sole structure 14 in other embodiments.

For equalization of gas pressure inside the opening 26 of the spacer 24,each pressure-sensing cell 18 comprises a ventilation hole 58 (bestshown in FIGS. 2 and 3). The ventilation holes 58 fluidly connect theinteriors of the pressure sensing cells to the outside, so thatcompression of the gas inside the pressure sensing cells is essentiallyavoided and thus has no significant impact on the response curve of eachcell 18. Additionally or alternatively, the ventilation holes 58 couldbe connected to a gas reservoir within the film-type pressure sensor.

FIG. 6 is a schematic block diagram of the flexible circuit of thepressure sensor 16. The pressure-sensing cells 18 are drawn as variableresistors 18.1-18.4. The cells are arranged electrically in parallelbetween a respective terminal 50.1, 50.2, 50.3 or 50.4 of the electroniccontrol module (not shown in FIG. 6) and circuit ground 52. Theelectronic control module determines the pressure values based upon theresistance (or the current or the voltage if one of these quantities iskept constant) measured between each terminal 50.1, 50.2, 50.3 or 50.4and circuit ground. It should be noted that the cell response curve isinfluenced by changes in resistivity of the electrode material, whichmay vary depending on ageing, temperature, humidity or otherenvironmental influences. To be able to correct or compensate suchinfluence on the pressure values, a reference resistor 54 is provided.The reference resistor 54 is made of the same material as the electrodes28, 30. It is arranged somewhere on the pressure sensor 16 so that itexperiences essentially the same environmental influences as theelectrodes 28, 30. In the illustrated embodiment, the reference resistor54 is arranged electrically between a reference terminal 56 and circuitground 52, in parallel to the pressure sensing cells. The electroniccontrol module measures the resistance of the reference resistor 54. Anydeviation from a nominal value is used to correct the readings of thepressure-sensing cells 18. The reference resistor 54 may be arranged oneither one of the carrier films 20, 22. One could also use a pluralityof resistors arranged on one or both of the carrier films. Anotherpossibility would be to provide a preloaded pressure-sensing cell (i.e.a pressure-sensing cell wherein the electrodes are permanently kept incontact).

The reference resistor 54 and the resistive electrodes 28, 30 of thepressure-sensing cells are preferably obtained by printing of carbon inkon the respective carrier film. The strip conductors 34, 36 arepreferably made of silver ink. The electrically insulating layer 32 ineach pressure-sensing cell 18 is preferably also a printed layer.Alternatively, the electrically insulating layer 32 could be laminatedon the carrier film and a resistive electrode.

FIG. 7 is a schematic block diagram of an alternative flexible circuitfor the pressure sensor 16. Unlike in the flexible circuit of FIG. 6,the reference resistor 54 is arranged electrically between circuitground 52 and the pressure-sensing cells 18, drawn again as variableresistors 18.1-18.4, in the manner of a voltage divider. During themeasurement, one pressure-sensing cell at a time may be connected to avoltage source (e.g. a battery) by means of its terminal 50.1, 50.2,50.3 or 50.4. The electronic control module determines the pressurevalues based upon the voltages measured on measurement terminal 60. Theresistance R_(x) of one of the pressure-sensing cells 18.1-18.4 may beobtained by R_(x)=R_(ref)(U₀/U_(meas)−1), where R_(ref) is theresistance of the reference resistor, U_(o) the voltage applied at theterminal 50.1, 50.2, 50.3 or 50.4, and U_(meas) the voltage measured atthe terminal 60. As one supposes that the resistances of thepressure-sensing cells and the reference resistors are subjected to thesame changes due to environmental influences (temperature, ageing,etc.), the normalized resistance R_(x)/R_(ref) is essentiallyindependent of these effects. In all other respects, the circuit for thepressure sensor 16 of FIG. 7 is configured and operates in the same wayas the one of FIG. 6.

FIG. 8 is a schematic block diagram of another alternative flexiblecircuit for the pressure sensor 16. According to this alternative, thereference resistor 54 is arranged in parallel with one of thepressure-sensing cells 18.1-18.4. In this arrangement, the referenceresistance is substantially higher than the resistances of thepressure-sensing cells 18.1-18.4 in actuated state (i.e. above theactivation pressure).

FIGS. 9 and 10 illustrate an alternative configuration of thepressure-sensing cells 18. FIG. 9 shows the arrangement of components onthe first carrier film 20, FIG. 10 the corresponding arrangement on thesecond carrier film 22. In this variant, the resistive electrodes 28, 30comprise a plurality of separate, generally triangular portions, whichprotrude in interdigitating manner from the long sides of thepressure-sensing cell 18 into the opening 26 so as to form arepetitionary pattern along the axis of main extension A of the cell.Each triangular portion of the second electrode 30 is disposed as thevertical projection of a corresponding triangular portion of the firstelectrode 28 (and vice-versa). The triangular portions of the firstelectrode 28 are contacted by the first strip conductor 34 outside ofthe opening 26 at their tops. The triangular portions of the secondelectrode 30 are contacted by the second strip conductor outside of theopening 26 at their bases. That arrangement forces currents to flowessentially perpendicular to the axis of main extension A. Theelectrically insulating layer 32 comprises a plurality of separate,spindle-shaped portions, each of which is arranged so as to cover thoseareas, in which the sides of neighboring triangular portions of thefirst electrode 28 run alongside one another. In all other respects, thepressure-sensing cell of FIGS. 9 and 10 is the same as and operates inthe same way as the pressure-sensing cell depicted in FIG. 3.

FIG. 11 is a top view of a variant 16′ of the pressure sensor 16′ ofFIG. 2. The pressure sensor 16′ is of identical configuration as thepressure sensor 16 of FIG. 2, except for the middle portion 62, wherethe pressure sensor 16′ is connected to the control module 46. Thepressure sensor 16 of FIG. 2 comprises two connection strips extendingalongside the electronic control module 46, which is mechanically andelectrically connected to the pressure sensor 16 by means of aconnection tongue 68. It has been found that such connections strips maybe subjected to buckling when the foot rolls off. Over time, bucklingmay lead to deterioration of the connection strips and any stripconductors arranged thereon. The buckling problem is significantlyreduced with the pressure sensor 16′ of FIG. 11. In the pressure sensor16′, the connection strip 64 that interconnects the forefoot portion ofthe sensor 16′ and the heel portion is passed underneath the electroniccontrol module 46.

FIG. 12 shows the longitudinal cross section C-C of FIG. 11. Theconnection strip 64 is guided though a trough-shaped receptacle 66 forthe electronic control module 46. The receptacle 66 is preferably madeof a plastic material (e.g. PET or epoxy). The wall thickness of thereceptacle 66 is such that it can withstand the stresses in the middlearea of the shoe without substantial deformation and/or breaking. Theconnection strip 64 is firmly bonded to the bottom of the receptacle 66,so that it is the receptacle 66 that takes up most of the strainsoccurring in this area during rolling off of the foot and so that theconnection strip 64 is prevented from ejecting the electronic controlmodule 46 out of the receptacle when tension is applied to it.

In the area of the connection strip 64, the upper (second) carrier filmof the pressure sensor is interrupted and detached from the spacer filmand the first carrier film in such a way that a tongue or flap 68′ isformed. This tongue or flap 68 carries those parts of the stripconductors 34, 36 which are connected to the electronic control module46. Preferably, the tongue or flap 68′ is equipped with a crimpconnector portion (not shown) to removably connect the electroniccontrol module 46 to the film structure of the pressure sensor 16′. Inthe connection strip 64, the strip conductors are all routed between thebottom (first) carrier film and the spacer. Accordingly, feedthroughcontacts are arranged to lead those strip conductors that are normallysandwiched between the second carrier film and the spacer to the firstcarrier film. Similar feedthrough contacts are provided to lead thosestrip conductors that are normally sandwiched between the first carrierfilm and the spacer to the tongue or flap 68′.

While specific embodiments have been described in detail, those withordinary skill in the art will appreciate that various modifications andalternatives to those details could be developed in light of the overallteachings of the disclosure. Accordingly, the particular arrangementsdisclosed are meant to be illustrative only and not limiting as to thescope of the invention, which is to be given the full breadth of theappended claims and any and all equivalents thereof.

Specifically, in the embodiment described in detail, thepressure-sensing cells 18 are configured as so-called through-modepressure-sensing cells. In these cells, the electrodes that are incontact with the conductors leading to each cell are arranged on thefirst and the second carrier film, respectively. Those skilled willunderstand that the pressure-sensing cells could also be configured asso-called shunt-mode pressure-sensing cells, wherein a first and a thirdelectrodes are in contact with the conductors leading to each cell andare arranged on the same carrier film. The second electrode is in thiscase a shunt element, which is brought into contact with the first andthe third electrode when pressure is applied. The electricallyinsulating layer in this case locally prevents a direct contact betweenthe first and the second electrode, and possibly also between the thirdand the second electrode.

1. An article of footwear, comprising a sole structure for supporting awearer's foot and an upper for holding the wearer's foot onto the solestructure, wherein said article of footwear comprises a pressure sensorarranged in said sole structure for measuring a pressure exerted by thewearer's foot on the sole structure, said pressure sensor comprising oneor more elongated pressure-sensing cells, each of said pressure sensingcells having an axis of main extension and comprising a first flexiblecarrier film and a second flexible carrier film, said first and secondcarrier films being attached to one another by a spacer film having anelongated opening oriented along said axis of main extension, a firstelectrode arranged on said first carrier film and a second electrodearranged on said second carrier film, at least one of said first andsecond electrodes made of resistive material, said first and secondelectrodes being arranged in facing relationship with each other in saidopening in such a way that said first and second electrodes may bebrought into contact with each other when pressure is exerted on saidpressure-sensing cell and that a contact area between said first andsecond electrode increases with increasing pressure, wherein anelectrically insulating layer is arranged within the opening of saidspacer, said electrically insulating layer having a shape so as tolocally prevent a direct contact between said first and secondelectrodes where said electrically insulating layer is present and toenable said direct contact where said electrically insulating layer isabsent, said shape being constant or repetitionary along said axis ofmain extension.
 2. Article of footwear as claimed in claim 1, whereinsaid one or more elongated sensor cells are located in said solestructure in areas expected to be subjected to pressure peaks when thewearer is standing still, is walking or is running.
 3. Article offootwear as claimed in claim 1, wherein each of said one or moreelongated sensor cells is located in an area corresponding to a bone orpart of bone of a wearer's foot selected from the heel bone, the head ofthe first metatarsal bone, the head of the fourth or fifth metatarsalbone, the head of the second or third metatarsal bone and the head ofthe first phalange.
 4. Article of footwear as claimed in claim 3,wherein the axis of main extension of each cell is oriented along avertical projection onto the sole structure of an axis of main extensionof the bone to which it corresponds.
 5. Article of footwear as claimedin claim 1, wherein each of said pressure sensing cells is oval,elliptical or rectangular with rounded angles.
 6. Article of footwear asclaimed in claim 1, wherein the shape of said electrically insulatinglayer comprises a sequence of generally triangular tooth portionsarranged in the manner of a toothed rack in parallel with said axis ofmain extension.
 7. Article of footwear as claimed in claim 1, whereinone of said first and second electrodes that is made of resistivematerial is made of graphite.
 8. Article of footwear as claimed in claim1, wherein said electrically insulating layer is made of electricallyinsulating ink.
 9. Article of footwear as claimed in claim 1, whereineach of said pressure sensing cells comprises a ventilation hole, incommunication with the exterior or a gas reservoir, for equalization ofgas pressure inside said opening.
 10. Article of footwear as claimed inclaim 1, wherein said sole structure comprises an insole, said pressuresensor being arranged on or in said insole.
 11. Article of footwear asclaimed in any one of claim 1, wherein said sole structure comprises amidsole, said pressure sensor being arranged on or in said midsole. 12.Article of footwear as claimed in claim 1, wherein said one or morepressure-sensing cells are at least two pressure-sensing cells, andwherein said pressure sensor comprises one or more connection stripsinterconnecting said at least two pressure sensing cells, said one ormore connection strips being integrally formed with said at least twopressure sensing cells, and said one or more connection strips bearingconductors for connecting the first and second electrodes of eachpressure-sensing cell with an electronic control module.
 13. Article offootwear as claimed in claim 12, wherein at least one of said connectionstrips has a serpentine shape.
 14. Article of footwear as claimed inclaim 1, wherein said article of footwear is a sports shoe.
 15. Apressure sensor for an article of footwear, comprising a flexiblemultilayer film structure that includes a forefoot portion, a heelportion and a connection strip that connects the forefoot portion to theheel portion, the connection strip being integrally formed with themultilayer film structure, wherein the pressure sensor further comprisesa trough-shaped receptacle for an electronic control module, whichreceptacle the connection strip is arranged across and bonded to. 16.Article of footwear as claimed in claim 1, wherein the first and secondelectrodes comprise a plurality of generally triangular portions, whichprotrude in interdigitating manner from long sides of thepressure-sensing cell into the opening so as to form a repetitionarypattern along the axis of main extension and wherein the electricallyinsulating layer comprises a plurality of separate, spindle-shapedportions, each of which is arranged so as to cover areas, in which sidesof neighbouring triangular portions of the first electrode run alongsideone another.